A typical static seal assembly has a first member with a first mating surface, an annular sealing ring of suitable sealing material (e.g., metal O-ring), and a second member with a second mating surface. A mechanical load is applied to the sealing ring through the first and second mating surfaces of the members. Typically, the mechanical load is created by torquing down a multitude of fasteners such that a displacement, also known as squeeze, occurs between the sealing surfaces. The net loading of the contact surfaces creates the two sealing lines.
The low leakage requirement can be achieved by compressing a solid metal ring of rectangular cross-section with a sufficient force. One problem with a solid metal ring is that the force created could be of sufficient magnitude to cause plastic deformation of the mating surfaces of the members. This plastic deformation of the mating surface is called brinelling. Once brinelled, the probability of proper resealing is drastically reduced without first repairing the damaged sealing surfaces.
The design requirements for static sealing therefore requires an optimum load level and flexibility. A good static seal when squeezed must be able to generate load levels large enough to seal, but not large enough to brinell the cavity surface. Currently, there are many types of metallic sealing rings in the prior art.
The metallic "O" rings were an early effort to meet these conflicting design requirements. However, the resiliency of this type of seal is rather limited because the "O" ring, whether solid or hollow, is usually too stiff, and is inherently expensive. The development of the C-shaped sealing ring was an improvement to the "O" ring. In particular, by simply discarding a portion of the "O", the hoop restraint of the seal is greatly reduced and the seal becomes more flexible. However, common "C" seals typically cannot reach the desirable standard vacuum level of 1.0E.sup.-9 standard (1 atmosphere) cubic centimeters (scc) He/sec. without modification and without being coated with very soft plating materials.
Moreover, the operating principle of the "C" seal is to create and maintain a narrow contact dam between the seal and cavity. Because the contact is localized, the force is also locally concentrated on the seal. Therefore, as long as the seal surface is softer than the cavity surface, the seal face will yield to achieve sealing. The metallic O-ring design utilizes the same principle. Both the "C" and "O" type seals maintain a narrow sealing line, which shifts as the seal is compressed to the working height.
In view of the above, it will be apparent to those skilled in the art that there exists a need for an improved sealing ring with wide sealing areas that minimizes brinelling and shifting of the sealing line. This invention addresses this need in the art as well as other needs which will become apparent to those skilled in the art once given this disclosure.